Just changed the head unit on my tridata. The B34 draws 1.9m but the sensor is mounted just forward of the keel (accessed at aft end of the forward bunk) to offset the depth to show true depth below the keel I need to know the distance between the sensor and the waterline .... I'm estimating about 500mm that would mean an offset of 1.4 m.
Has anybody measured it with this same configuration?
If you want to know the depth under the keel, you do not need the distance from waterline to transducer. Offset can be positive, negative or zero. In your case, for depth under the keel, you need a negative offset (keel's depth).
One quick way to go about it is to use some drawings from owner's manual and match up a known distance (waterline, boat LOA, draft, etc. ) as a reference and measure the distance you want. It's not perfect but i would say it falls within 10 cm range or less.
We also draw1.9m, but we set the sounder to display actual depth and not depth below the keel...
We set it by the use of a 'lead line' (a weighty shackle on a light nylon line) in a shallow anchorage and set the sounder to read the actual depth we measured...
Setting the actual depth is just a personal preference, others like to set depth below the keel, using a weighted line means you don't actually have to know the depth of your transducer to use either setting..
Thanks for the response
"If you want to know the depth under the keel, you do not need the distance from waterline to transducer. Offset can be positive, negative or zero. In your case, for depth under the keel, you need a negative offset (keel's depth).
One quick way to go about it is to use some drawings from owner's manual and match up a known distance (waterline, boat LOA, draft, etc. ) as a reference and measure the distance you want. It's not perfect but i would say it falls within 10 cm range or less."
The 1.9m I know what I am after is the distance from the transducer to the waterline which I plan to subtract from the 1.9 which will give me a displayed true depth below the keel. I have estimated this currently but I suspect this is a factory fitted sensor so others must have this measurement.
If it helps, looks like 0.4m.
Great thanks this is just what I needed